Music synthesis generally operates by taking a control stream such as MIDI input and generating sound associated with that input. MIDI inputs include the instrument to play, pitch, and loudness. Other MIDI inputs may include MIDI modulation control, and vibrato speed.
Simply generating a signal that has the correct pitch and loudness produces a very poor, synthetic sound. All music needs time varying elements, such vibrato, to sound natural.
In addition, natural music does not switch abruptly between one note and another in a step-wise fashion. Rather, there is a period of transition, starting before the changeover from one note to the next begins and continuing for some time after the changeover ends.
In addition, the contour of a note as it changes over time, and the shape of the transition from one note to the next, is highly dependent on the context of the note within a musical phrase. Just as a skilled reader processes written text as phrases rather than individual words or syllables, a skilled instrumentalist processes groups of notes as musical phrases. The musical phrase forms a single shape or acoustic gesture in the mind of the performer. This shape is translated, almost unconsciously, into detailed physical actions on the instrument. Connecting notes to form phrases is essential to expressive performance.
U.S. Pat. No. 6,316,710 to Lindemann describes a synthesis method which stores segments of recorded sounds, particularly including transitions between musical notes, as well as attack, sustain and release segments. These segments are sequenced and combined to form an output signal. U.S. Pat. No. 6,298,322 to Lindemann describes a synthesis method which uses dominant sinusoids combined with a vector-quantized residual signal. U.S. Pat. No. 6,111,183 to Lindemann describes a synthesizer which models the time varying spectrum of the synthesized signal based on a probabilistic estimation conditioned to time-varying pitch and loudness inputs.
A need remains in the art for improved methods and apparatus for transitioning between successive notes in a natural and expressive manner, and for shaping notes as a function of their context within a musical phrase.